「谈到魔鬼」是什么意思呀？

speak of the devil 

说曹操，曹操到

Speak of the devil ! Look who's here !

真是说曹操，曹操就到了！看看谁来了！

A : A co-worker of mine is a part-time fashion designer. I often go shopping with him because he has good taste in fashion.

B : Hey ! Olivia, wanna go shopping with me tonight ? Oh my God ! The mall is having a big clearance sale. Yeah !

A : Speak of the devil !

A : 我的一个同事平时也兼职做服装设计师，他很有品味噢，我们经常一起去逛街。

B : Hey, Olivia, 今晚要跟我一起去逛街吗？天呀！商场在做清仓大甩卖耶！Yeah !

A : 哈，真的是说曹操，曹操就到了！